The Failed Serotonin Theory of Depression: A Marxist Analysis

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From Venezuela and made by Venezuelan Chavistas
By Carlos L. Garrido – Sep 9, 2022
A recent study published in the journal Molecular Psychiatry sent shockwaves across the scientific community and popular outlets as it disproved the predominant âserotonin hypothesisâ of depression. In just two weeks since its publication it has been accessed by nearly half a million people and the subject of dozens of subsequent articles. The researchers analyzed a total of seventeen systematic reviews, meta-analyses, and other large studies focused on the following six tenets pertinent to the âserotonin hypothesisâ of depression:
â(1) Serotonin and the serotonin metabolite 5-HIAAâwhether there are lower levels of serotonin and 5-HIAA in body fluids in depression; (2) Receptorsâwhether serotonin receptor levels are altered in people with depression; (3) The serotonin transporter (SERT)âwhether there are higher levels of the serotonin transporter in people with depression (which would lower synaptic levels of serotonin); (4) Depletion studiesâwhether tryptophan depletion (which lowers available serotonin) can induce depression; (5) SERT geneâwhether there are higher levels of the serotonin transporter gene in people with depression; (6) Whether there is an interaction between the SERT gene and stress in depression.â1
None of the studies were able to prove any significant link between serotonin levels and depression based on the above tenets, leading the researchers to conclude that âthere is no convincing evidence that depression is associated with, or caused by, lower serotonin concentrations or activity.â2
The researchers further argue, âThe idea that depression is the result of abnormalities in brain chemicals, particularly serotonin (5-hydroxytryptamine or 5-HT), has been influential for decades,â such that today â80% or more of the general public now believe it is established that depression is caused by a âchemical imbalance.â3Â In light of this finding, one must askâhow did a hypothesis which failed to substantially prove the connection it is based on achieve such general acceptance?
The serotonin hypothesis wasnât always the dominant explanation for depression. Shortly after the Second World War, âthe first antipsychotic, chlorpromazine, was synthesized when chlorine was added to the promethazine structure.â4Â This synthesis formed âthe basis of the development of the first antidepressantsâ which emerged following Roland Kuhnâs 1957 presentation in the World Psychiatric Association Meeting, where shortly after the first tricyclic antidepressant was released for clinical use in Switzerland.5
A decade later, in the mid-1960s, a series of studies introduced serotonin as the âmolecule behind depression.â These studies culminated in the work of Lapin and Oxenkrug, who postulated in 1969 the âserotonergic theory of depression, which was based on a deficit of serotonin at an inter-synaptic level in certain brain regions.â6 In the following years, the pharmaceutical company Eli Lilly created a serotonin-depression study team, which found that fluoxetine hydrochloride was âthe most powerful⌠selective inhibitor of serotonin uptake among all the compounds developed.â7 The results led to the 1987 Food and Drug Administration (FDA) approval of the clinical usage of Prozac (the brand name given to fluoxetine), the first major selective serotonin receptor inhibitor (SSRI) antidepressant drug.8
Prozac became the drug of the age, a commodity which, like Brave New Worldâs soma, could provide direct, unmediated happiness.
The release of Prozac revolutionized the commodification of medicine, incorporating a new field of mass advertisement which has since become the norm. However, as the documentary, Prozac: A Revolution in a Capsule demonstrates, the drug obtained its prominence not only through advertisementâwhich, interestingly enough, first occurred through business and finance magazinesâbut through its incorporation into culture as an iconic symbol of the zeitgeist.9 From Woody Allen movies to The Sopranos to late night talks shows, Prozac became the drug of the age, a commodity which, like Brave New Worldâs soma, could provide direct, unmediated happiness. This quickly resulted in the âProzac boom,â making it by 1990 the most prescribed drug in the United States, and within ten years of its 1988 release, visits to the doctor for depression doubled and the prescribing of antidepressants tripled.10
The association of depression with low levels of serotonin was an intentional result of institutionally supported (e.g., American Psychiatric Organization) marketing campaigns from the pharmaceutical industry. This has provided âan important justification for the use of antidepressantsâ and perpetuated an antidepressant drug market that was valued at almost $16 billion in 2020 (a number expected to rise to $21 billion by the end of the decade);11Â in todayâs antidepressant epidemic, one in six Americans are on antidepressants.12Â This phenomenon cannot be understood separately from the general commodification and marketization of medicine. As Joanne Moncrieff has argued, âthere are some obvious drivers of this trend, such as the pharmaceutical industry, whose marketing activities have been facilitated both by the arrival of the Internet, and political deregulation, including the repeal of the prohibition on advertising to consumers in the US and some other countries in the 1990s.â13
This is how and why the serotonin theory gained and sustained its hegemony since the 1990s. However, within the scientific community this hypothesis has been on the chopping block for almost two decades as individual studies have disconfirmed various parts of the hypothesis. The scientific community, in general, is much more skeptical of the âserotonin hypothesisâ than the general public. This disconnection between the much more nuanced science on depression and the public perception of the issue has been the subject of various articles and speaks to both the separation of science from everyday life and to the effectiveness of medical marketization.14Â Nonetheless, the explosion the recent study caused is a result of its comprehensive character as an âumbrella reviewâ which examined all parts of the serotonin hypothesis at onceâand in doing so, went well beyond the many studies which have focused on separate parts in the last couple of decades.
From Biochemical Determinism to Dialectical Materialism
There is a prevalent myth which holds that those who function in society as professional âintellectualsâ are somehow âautonomous and independentâ from the dominant social order and the interests of the ruling class.15 This myth predominates in the community of the âhardâ sciences perhaps more than in any level of traditional intellectuals. Here it is taken as sensum communem that science is objective and disconnected from ideology and social factors. For these folks, as Marxist scientists Richard Levins and Richard Lewontin said, ânothing evokes as much hostility⌠as the suggestion that social forces influence or even dictate either the scientific method or the facts and theories of science.â16 But it is in this illusion of non-ideological objectivity where ideology can be seen to be the most entrenched, functioning as unknown knowns, that is, as unrecognized assumptions or inherent biases which mediate how scientists approach the world.
This does not mean, as the postmodernist disease17 which influences some of the philosophy of science holds, that we should maintain a âdeep epistemological skepticismâ which often, as Ellen Meiksins Wood notes, conflates âthe forms of knowledge with its objects⌠as if they are saying not only that, for instance, the science of physics is a historical construct, which has varied over time and in different social contexts, but that the laws of nature are themselves âsocially constructedâ and historically variable.â18
On the contrary, in Marxism, as Helena Sheehan argues, there is âno conflict between [stressing] the historical and contextual nature of science and [affirming] the rationality of science and the overall progressive character of its development.â19 In essence, the Marxist traditionâs understanding of the socially determined character of scientific production does not mean that scientific objectivity is rejected and that the object of scientific study itself is conceived of as relative. The form of abstract and unmediated objectivism which prevails in the sciences is rejected and what is affirmed is a necessarily socially mediated understanding of scientific objectivity. This overcomes, as Sheehan notes, the stale âobjectivist/constructivistâ binary which today structures the discourse about science and affirms instead a dialectical both/and attitude.20 This is important to clarify so that the forthcoming analysis of capitalismâs influence on science is not confused as an embracement of relativism and a rejection of scienceâs ability to produce objective knowledge of the world.
The serotonin hypothesis emerges from what Levins and Lewontin called âCartesian reductionismâ (the objectivist extreme), which they held to be the âdominant mode of analysisâ in all spheres of todayâs sciences. In psychiatry this shows up as genetic and biochemical determinism, an attempt to reduce the complexity of mental health issues to genetics or to biochemical mechanisms which, with respect to the latter, somehow the major pharmaceutical companies always have a pill for. But, as Moncrieff has argued, âmental health problems are not equivalent to physical, medical conditions and are more fruitfully viewed as problems of communities or societies.â21
Reductionism, in essence, is a methodological reflection in the sciences of bourgeois individualism and Robinsonade forms of thinking, which artificially divorce individuals from society and hold the latter to be simply the sum of the former.
For instance, studies have shown that âwithin a given location, those with the lowest incomes are typically 1.5 to 3 times more likely than the rich to experience depression or anxiety.â22Â The plethora of factors that stem from and contribute to poverty has allowed researchers to establish âa bidirectional causal relationship between poverty and mental illness,â such that poverty both increases the likelihood of mental illness and is proliferated further by it.23Â The fact that the poorest in any context are up to three times more likely to experience depression than the rich shows that any analysis of depression must necessarily take into account the socioeconomic context of the individual. This inequality induced dissatisfaction allows one to understand both poverty and depression relationally. As Marx had already noted in 1847,
Our desires and pleasures spring from society; we measure them, therefore, by society and not by the objects which serve for their satisfaction. Because they are of a social nature, they are of a relative nature⌠A house may be large or small; as long as the surrounding houses are equally small it satisfies all social demands for a dwelling. But let a palace arise beside the little house, and it shrinks from a little house to a hut⌠if the neighboring palace grows to an equal or even greater extent, the occupant of the relatively small house will feel more and more uncomfortable, dissatisfied and cramped within its four walls.24
The Cartesian reductive framework contains various methodological flaws which prevent the concrete understanding of the world. It treats, for instance, the interactions of parts and whole one-sidedlyâas if parts are homogenous entities ontologically prior to the whole, and hence, as if the whole was simply the sum of its parts. In so doing, this outlook draws artificial hard and fast lines between causes and effects and fails to see how parts and wholes are reciprocally conditioning, i.e., how âtheir very interaction structures the way they are interrelated and interpenetrated, resulting in what is called a whole.â25Â In short, how wholes are not simply the sum of their parts, but the totalities through which the parts themselves attain the functions which form the whole. It is, in essence, a methodological reflection in the sciences of bourgeois individualism and Robinsonade26Â forms of thinking, which artificially divorce individuals from society and hold the latter to be simply the sum of the former.
However, biochemical determinism/reductionism does not necessarily have to reduce explanations to only one factor. For instance, the inconsistent success of SSRIs27 in treating depression has led some scientists to sustain ex juvantibus28 (from reasoning backwards) that serotoninâs role in depression is interactive and dependent on its relations with adrenaline, dopamine, and other chemical processes. Although this represents a more complex view of the serotonin hypothesis in particular, and of the often wrongly conflated âchemical imbalanceâ view of depression, it is nonetheless a form of biochemical determinism.29 This is because it fails to see how the âchemical imbalancesâ donât arise out of a void but are produced by the concrete environment the individual is in. The point, again, is not to diminish the biochemical in order to elevate the role of the environment, but to see both the biochemical and the environment as dialectically interconnected, acting âupon each other through the medium of the [individual].â30 As Levins and Lewontin argue, the individual âcannot be regarded as simply the passive object of autonomous internal (biochemical composition/genes) and external (environment) forces;â instead, the individual functions as a subject-object which is both conditioned by these factors (as object) and reciprocally conditions them (as subject).31
The limitations of the prevalent serotonin hypothesis also helps to demonstrate what Friedrich Engels noted in his unfinished Dialectics of Nature: although ânatural scientists believe that they free themselves from philosophy by ignoring it or abusing it⌠they are no less in bondage to philosophy but unfortunately in most cases to the worst philosophy.â32 This reductive, bio-determinist outlook straitjackets science within abstract thought, preventing it from seeing things in their movements and interconnections. It forces the reduction of larger problems to simple componentsâsince these are seen as the ontological basis of wholesâand limits the possibility of observing issues like depression dynamically and comprehensively.
It is much easier to reduce depression to a biochemical phenomenon in the brain than to analyze how the social relations prevalent in the capitalist mode of life create the conditions for the emergence of depression. Similarly, once this reduction is established, it is much easier to treat the âsolutionâ through individualized drug consumption than through socially organized revolutionary activity. As Moncrieff has argued, âby obscuring [the] political natureâ of mental illness, certain âcontentious social activitiesâ are enabled, and attention is diverted âfrom the failings of the underlying economic system.â33
Tracing depression to the exploitative and alienating relations sustained between people and their work, their peers, and nature, is not only a much more laborious task, but one which would necessarily end in the realization of the systemic root of the problem. Given capitalismâs universal commodification, and the form this takes in what Levins and Lewontin call the âcommoditization of science,â such a result is directly against the interests of the institutions that control scientific knowledge production.34Â As one of many other fields in which the universalizing logic of commodity production has penetrated, the aim is, of course, profitability; the quest for truth and scientific discovery is subsumed under the quest for profit. This is especially true after four decades of neoliberalism, where, as Moncrieff notes, âmore and more aspects of human feelings and behaviourâ have been commodified and turned âinto a source of profit for the pharmaceutical and healthcare industries.â35Â âInvesting in research,â as Levins and Lewontin argue, is but âone of several ways of investing in capital.â36
In the West, this reality was clear to the rich tradition of British Marxists scientists like J.B.S. Haldane, J.D. Bernal, Hyman Levy, and others which emerged following the 1931 Second International Congress of the History of Science and Technology. As J.D. Bernal stated in 1937, âproduction for profit can never develop the full potentialities of science except for destructive purposes,â only âthe Marxist understanding of science puts it in practice at the service of the community and at the same time makes science itself part of the cultural heritage of the whole people and not of an artificially selected minority.â37
Healthcare for Human Rights, Not Profits: what the US Can Learn from Cubaâs Coronavirus Response
Towards Socialist Science and Medicine
The serotonin theory gained prominence because: 1) it fits within the one-factor, causally linear framework of the Cartesian reductionist outlook prevalent in mainstream science; 2) it was a diagnosis which facilitated the greatly profitable solution embodied in the tens of billions of dollarsâ worth antidepressant drug industry; 3) it plays a hegemonic role in steering the diagnosis of the depression epidemic away from its real sourceâcapitalist social relations which sustain the mass of people alienated from what they produce, from other people, and from natureâand, specifically with respect to the United States, in drowning debt for getting sick, pursuing an education, or attempting to own a home.
Socialism removes these material difficulties upon which many mental health issues are grounded and places the working class in control of the economy, state, and civil institutions, making them function in the service of human and planetary needs, not profit. By abolishing poverty and war; guaranteeing healthcare, housing, and education as a right for all; providing everyone with meaningful well-paying jobs; amongst other things, a socialist society creates the economic and social security which radically transforms the environment in which most cases of depression are rooted. If one seriously seeks to overcome the depression epidemic capitalism is hurling the mass of people into, socialism is the only real solution.
In Cuba, mental health treatment emphasizes âindividual and group psychotherapiesâ of various kinds and incorporates psychopharmacology in an integrated fashion with the former.
Likewise, only socialism can de-commodify science and provide the general social atmosphere for a move away from a hegemonic outlook dominated by static, reductive, abstract, individualist, irrationalist, deterministic, and binary thought, and towards a dialectical materialist one which emphasizes change, interconnection, reciprocity, sociality, emergence, and concrete investigation of the concrete.38Â The extraordinary successes of Cuban science and medicine testify to what can be done when the profit motive is removed and comprehensive, preventative, and community-based care becomes the norm.
While enduring an internationally denounced blockade from the most formidable of empires, the Cuban revolutionâs commitment to a science for the people has allowed it to construct what is internationally recognized as one of the best health care systems in the world.39Â Cubaâs comprehensive social care emphasizes the impact of biological, social, cultural, economic and environmental factors on patients. Far from the United Statesâ drug-first approach of dealing with mental health issues, Cubaâs comprehensive social care allows all medical issues to be better understood at their source, treated, and prevented from occurring.40Â In Cuba, mental health treatment emphasizes âindividual and group psychotherapiesâ of various kinds,41Â and when not hampered by the blockade, incorporates psychopharmacology in an integrated fashion with the former.42
Cuban scientists see mental health issues and treatment âwithin the context of the community,â not isolated individuals.43Â As Alexis Lorenzo Ruiz, president of the Cuban Society of Psychology, said: âAt all times, the communityâlike the familyâare participants and necessary contributors in each action taken to move toward an improvement in the wellbeing of people with mental illness.â44Â Additionally, unlike the disease-centered model of care which predominates in most capitalist countries, this human-centered approach promotes multidisciplinary and integrative relations between mental and medical care within the different fields of medicineâvarious forms of medical doctors, psychologists, nurses, and other health care professionals train side by side each other within the communities they serve in.45Â This socialist model has afforded the Cuban people the conditions where, despite the enormous material difficulties created by the US blockade, depression in Cuba affects only 3.8 percent of the population, whereas in the United States 4.8 percent.46
In their 1985 book, The Dialectical Biologist, Levins and Lewontin reformulate Marxâs Eleventh Thesis and state that âdialectical philosophers have thus far only explained science. The problem, however, is to change it.â47 In the West, the seeds of such a change are emerging once again. As Nafis Hasan wrote in Science for the People, ârecent developments in the fields of immunology, cancer, theoretical and evolutionary biology lend credenceâ to the view that âany non-reductionist approach (e.g., systems biology) to studying biology will advertently end up using a dialectical approach.â48 The fall of the reductive serotonin hypothesis in depression research is but one instance in many pointing to the fact that the dominant outlook presents a fetter for the development of the sciences. Just like a socialist revolution is needed to free humanity and the forces of production from the fetters of the capitalist system of waste, a revolution in outlook is needed to free the sciences from its archaic Cartesian reductionism and furnish it with âthe most scientifically apt method for understanding the worldââdialectical materialism.49
Carlos L. Garrido is a Cuban American philosophy instructor at Southern Illinois University, Carbondale. He is the director of the Midwestern Marx Institute and the author of The Purity Fetish and the Crisis of Western Marxism (2023), Marxism and the Dialectical Materialist Worldview (2022), and the forthcoming Hegel, Marxism, and Dialectics (2024). He has written for dozens of scholarly and popular publications around the world and runs various live-broadcast shows for the Midwestern Marx Institute YouTube. You can subscribe to his Philosophy in Crisis Substack HERE.
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